In recent years, in lighting devices, an LED module configured by a plurality of LEDs (light emitting diodes) is used as a light source, and there is known an LED driving device that performs lighting by dimming-controlling of the LED light source.
Such an LED driving device is described, for example, in JP-A-2009-123681. Specifically, the LED driving device is provided with a constant current circuit having a switching element, and the LED driving device supplies an LED current to the LED module to turn on the LED light source by turning on-and-off at predetermined intervals the switching element. By performing PWM (pulse width modulation) control, the LED driving device performs the dimming control for the LED light source. The PWM control is performed by changing the on-duty ratio of the PWM signal corresponding to the occupied ratio of the time period during which the switching element is turned on with respect to a predetermined period.